CATALYTIC CONVERTER

2001 Toyota Celica • 4 cylinder 2WD Manual • 136,000 miles

I have a toyota celica gt with 1.8L 1zz fe, what catalytic converter should I replace it with, and should I replace the O2 sensors while im doing so or should I use the old O2 sensors? Which O2 sensors should I use the universal ones or the denso ones? Or does it matter?

You could get a performance catalyc converter or just the OEM one. Myself I don't like universal catalyc converters, because sometimes there has to be a mod. Done. Are your O2 sensors throwing any codes yet? But, is really up to you. You can replace them anyways. The denso, should be good. : )
Hope this helps.